I don't get it at all, how is D4 (considerably) "better"?

D4
Higher framerate , yes

One stop better ISO capability (not considered at the same output size which narrows the gap considerably)
Better built and longer lasting shutter - probably
Built in vertical grip
The odd bell and whistle I'm sure.

Easily (and I'm not talking in general use as it differs from photographer to photographer, but on cost calculation basis) countered by this imo:

D800
More than double the pixel number.
Smaller/lighter
built in flash (this is a good thing, otherwise just glue it shut)
USB 3 (as opposed to USB 2) 10 times faster
Optional anti aliasing free sensor.

I don't get it. Who would've raised an eyebrow if they came in the same body and cost the same (or D4 less!) but now it's more than twice as expensive .

When the D3x came out it was to the D3s what the D800 is to the D4 and the price is reversed.

Go figure, I don't get it, but I'm not complaining (as I'm not getting the D4, but the D800), but I'm very surprised.

end rant